Wrap-around trench contact structure and methods of fabrication

Abstract

A wrap-around source/drain trench contact structure is described. A plurality of semiconductor fins extend from a semiconductor substrate. A channel region is disposed in each fin between a pair of source/drain regions. An epitaxial semiconductor layer covers the top surface and sidewall surfaces of each fin over the source/drain regions, defining high aspect ratio gaps between adjacent fins. A pair of source/drain trench contacts are electrically coupled to the epitaxial semiconductor layers. The source/drain trench contacts comprise a conformal metal layer and a fill metal. The conformal metal layer conforms to the epitaxial semiconductor layers. The fill metal comprises a plug and a barrier layer, wherein the plug fills a contact trench formed above the fins and the conformal metal layer, and the barrier layer lines the plug to prevent interdiffusion of the conformal metal layer material and plug material.

What is claimed is: 
     
       1. An integrated circuit structure, comprising:
 a semiconductor substrate having a first semiconductor fin and a second semiconductor fin protruding therefrom; 
 a trench isolation layer on the semiconductor substrate around a lower portion of the first semiconductor fin and around a lower portion of the second semiconductor fin, wherein an upper portion of the first semiconductor fin and an upper portion of the second semiconductor fin extend above the trench isolation layer; 
 a gate structure over the upper portion of the first semiconductor fin and over the upper portion of the second semiconductor fin, the gate structure having a first side and a second side; 
 a first epitaxial layer on the upper portion of the first semiconductor fin at the first side of the gate structure; 
 a second epitaxial layer on the upper portion of the second semiconductor fin at the first side of the gate structure, the second epitaxial layer discontinuous from the first epitaxial layer, wherein there is no silicide between the first epitaxial layer and the second epitaxial layer; 
 a contact metal over the first epitaxial layer and over the second epitaxial layer, the contact metal between the first and second epitaxial layers, the contact metal on a first portion of the trench isolation layer between the first epitaxial layer and the second epitaxial layer, and the contact metal having an uppermost surface, wherein the contact metal is not a silicide; and 
 a dielectric spacer between the contact metal and the gate structure, the dielectric spacer having an uppermost surface at a same level as the uppermost surface of the contact metal. 
 
     
     
       2. The integrated circuit structure of  claim 1 , wherein the contact metal is directly on the first epitaxial layer and directly on the second epitaxial layer. 
     
     
       3. The integrated circuit structure of  claim 1 , wherein the contact metal extends from the first portion of the trench isolation layer to a height above the first and second epitaxial layers, and wherein the contact metal completely fills a gap between the first epitaxial layer and the second epitaxial layer. 
     
     
       4. The integrated circuit structure of  claim 1 , wherein the first and second semiconductor fins comprise silicon, and wherein the first and second epitaxial layers comprise silicon and germanium. 
     
     
       5. The integrated circuit structure of  claim 1 , further comprising:
 a third epitaxial layer on the upper portion of the first semiconductor fin at the second side of the gate structure; 
 a fourth epitaxial layer on the upper portion of the second semiconductor fin at the second side of the gate structure, the fourth epitaxial layer discontinuous from the third epitaxial layer; and 
 a second contact metal over the third epitaxial layer and over the fourth epitaxial layer, the second contact metal between the third and fourth epitaxial layers, and the second contact metal on a second portion of the trench isolation layer between the third epitaxial layer and the fourth epitaxial layer. 
 
     
     
       6. The integrated circuit structure of  claim 5 , wherein the second contact metal is directly on the third epitaxial layer and directly on the fourth epitaxial layer. 
     
     
       7. A method of fabricating an integrated circuit structure, the method comprising:
 forming a first semiconductor fin and a second semiconductor fin protruding from a semiconductor substrate; 
 forming a trench isolation layer on the semiconductor substrate around a lower portion of the first semiconductor fin and around a lower portion of the second semiconductor fin, wherein an upper portion of the first semiconductor fin and an upper portion of the second semiconductor fin extend above the trench isolation layer; 
 forming a gate structure over the upper portion of the first semiconductor fin and over the upper portion of the second semiconductor fin, the gate structure having a first side and a second side; 
 forming a first epitaxial layer on the upper portion of the first semiconductor fin at the first side of the gate structure; 
 forming a second epitaxial layer on the upper portion of the second semiconductor fin at the first side of the gate structure, the second epitaxial layer discontinuous from the first epitaxial layer, wherein there is no silicide between the first epitaxial layer and the second epitaxial layer; 
 forming a contact metal over the first epitaxial layer and over the second epitaxial layer, the contact metal between the first and second epitaxial layers, the contact metal on a first portion of the trench isolation layer between the first epitaxial layer and the second epitaxial layer, and the contact metal having an uppermost surface, wherein the contact metal is not a silicide; and 
 forming a dielectric spacer between the contact metal and the gate structure, the dielectric spacer having an uppermost surface at a same level as the uppermost surface of the contact metal. 
 
     
     
       8. The method of  claim 7 , wherein the contact metal is directly on the first epitaxial layer and directly on the second epitaxial layer. 
     
     
       9. The method of  claim 7 , wherein the contact metal extends from the first portion of the trench isolation layer to a height above the first and second epitaxial layers, and wherein the contact metal completely fills a gap between the first epitaxial layer and the second epitaxial layer. 
     
     
       10. The method of  claim 7 , wherein the first and second semiconductor fins comprise silicon, and wherein the first and second epitaxial layers comprise silicon and germanium. 
     
     
       11. The method of  claim 7 , further comprising:
 forming a third epitaxial layer on the upper portion of the first semiconductor fin at the second side of the gate structure; 
 forming a fourth epitaxial layer on the upper portion of the second semiconductor fin at the second side of the gate structure, the fourth epitaxial layer discontinuous from the third epitaxial layer; and 
 forming a second contact metal over the third epitaxial layer and over the fourth epitaxial layer, the second contact metal between the third and fourth epitaxial layers, and the second contact metal on a second portion of the trench isolation layer between the third epitaxial layer and the fourth epitaxial layer. 
 
     
     
       12. The method of  claim 11 , wherein the second contact metal is directly on the third epitaxial layer and directly on the fourth epitaxial layer. 
     
     
       13. A computing device, comprising:
 a board; and 
 a component coupled to the board, the component including an integrated circuit structure, comprising:
 a semiconductor substrate having a first semiconductor fin and a second semiconductor fin protruding therefrom; 
 a trench isolation layer on the semiconductor substrate around a lower portion of the first semiconductor fin and around a lower portion of the second semiconductor fin, wherein an upper portion of the first semiconductor fin and an upper portion of the second semiconductor fin extend above the trench isolation layer; 
 a gate structure over the upper portion of the first semiconductor fin and over the upper portion of the second semiconductor fin, the gate structure having a first side and a second side; 
 a first epitaxial layer on the upper portion of the first semiconductor fin at the first side of the gate structure; 
 a second epitaxial layer on the upper portion of the second semiconductor fin at the first side of the gate structure, the second epitaxial layer discontinuous from the first epitaxial layer, wherein there is no silicide between the first epitaxial layer and the second epitaxial layer; 
 a contact metal over the first epitaxial layer and over the second epitaxial layer, the contact metal between the first and second epitaxial layers, the contact metal on a first portion of the trench isolation layer between the first epitaxial layer and the second epitaxial layer, and the contact metal having an uppermost surface, wherein the contact metal is not a silicide; and 
 a dielectric spacer between the contact metal and the gate structure, the dielectric spacer having an uppermost surface at a same level as the uppermost surface of the contact metal. 
 
 
     
     
       14. The computing device of  claim 13 , further comprising:
 a memory coupled to the board. 
 
     
     
       15. The computing device of  claim 13 , further comprising:
 a communication chip coupled to the board. 
 
     
     
       16. The computing device of  claim 13 , further comprising:
 a camera coupled to the board. 
 
     
     
       17. The computing device of  claim 13 , further comprising:
 a battery coupled to the board. 
 
     
     
       18. The computing device of  claim 13 , further comprising:
 an antenna coupled to the board. 
 
     
     
       19. The computing device of  claim 13 , wherein the component is a packaged integrated circuit die. 
     
     
       20. The computing device of  claim 13 , wherein the computing device is selected from the group consisting of a mobile phone, a laptop, a desk top computer, a server, and a set-top box.